Memory device and manufacturing method thereof

ABSTRACT

A memory device includes a substrate, a memory unit, and a first spacer layer. The memory unit is disposed on the substrate, and the memory unit includes a first electrode, a second electrode, and a memory material layer. The second electrode is disposed above the first electrode in a vertical direction, and the memory material layer is disposed between the first electrode and the second electrode in the vertical direction. The first spacer layer is disposed on a sidewall of the memory unit. The first spacer layer includes a first portion and a second portion. The first portion is disposed on a sidewall of the first electrode, the second portion is disposed on a sidewall of the second electrode, and a thickness of the second portion in a horizontal direction is greater than a thickness of the first portion in the horizontal direction.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a memory device and a manufacturingmethod thereof, and more particularly, to a memory device including aspacer layer and a manufacturing method thereof.

2. Description of the Prior Art

Semiconductor memory devices are used in computer and electronicsindustries as a means for retaining digital information or data.Typically, the semiconductor memory devices are divided into volatileand non-volatile memory devices. The volatile memory device is acomputer memory that loses its stored data when power to the operationis interrupted. Comparatively, in the non-volatile memory device, thestored data will not be lost when the power supply is interrupted. Forexample, resistive random access memory (RRAM) is a kind of non-volatilememory technology having the characteristics of low operating voltage,low power consumption, and high writing speed and is regarded as amemory structure that can be applied to many electronic devices.

SUMMARY OF THE INVENTION

A memory device and a manufacturing method thereof are provided in thepresent invention. A spacer layer is formed on a sidewall of a memoryunit, and the spacer layer formed on a sidewall of an upper electrode inthe memory unit is relatively thicker for protecting the memory unit insubsequent processes and improving manufacturing yield of the memorydevice accordingly.

According to an embodiment of the present invention, a memory device isprovided. The memory device includes a substrate, a memory unit, and afirst spacer layer. The memory unit is disposed on the substrate, andthe memory unit includes a first electrode, a second electrode, and amemory material layer. The second electrode is disposed above the firstelectrode in a vertical direction, and the memory material layer isdisposed between the first electrode and the second electrode in thevertical direction. The first spacer layer is disposed on a sidewall ofthe memory unit, and the first spacer layer includes a first portion anda second portion. The first portion is disposed on a sidewall of thefirst electrode, and the second portion is disposed on a sidewall of thesecond electrode. A thickness of the second portion in a horizontaldirection is greater than a thickness of the first portion in thehorizontal direction.

According to an embodiment of the present invention, a manufacturingmethod of a memory device is provided. The manufacturing method includesthe following steps. A memory unit is formed on a substrate, and thememory unit includes a first electrode, a second electrode, and a memorymaterial layer. The second electrode is disposed above the firstelectrode in a vertical direction, and the memory material layer isdisposed between the first electrode and the second electrode in thevertical direction. A first spacer layer is formed on a sidewall of thememory unit, and the first spacer layer includes a first portion and asecond portion. The first portion is disposed on a sidewall of the firstelectrode, and the second portion is disposed on a sidewall of thesecond electrode. A thickness of the second portion in a horizontaldirection is greater than a thickness of the first portion in thehorizontal direction.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing illustrating a memory device according toan embodiment of the present invention.

FIGS. 2-6 are schematic drawings illustrating a manufacturing method ofa memory device according to an embodiment of the present invention,wherein FIG. 3 is a schematic drawing in a step subsequent to FIG. 2 ,FIG. 4 is a schematic drawing in a step subsequent to FIG. 3 , FIG. 5 isa schematic drawing in a step subsequent to FIG. 4 , and FIG. 6 is aschematic drawing in a step subsequent to FIG. 5 .

DETAILED DESCRIPTION

The present invention has been particularly shown and described withrespect to certain embodiments and specific features thereof. Theembodiments set forth herein below are to be taken as illustrativerather than limiting. It should be readily apparent to those of ordinaryskill in the art that various changes and modifications in form anddetail may be made without departing from the spirit and scope of thepresent invention.

Before the further description of the preferred embodiment, the specificterms used throughout the text will be described below.

The terms “on,” “above,” and “over” used herein should be interpreted inthe broadest manner such that “on” not only means “directly on”something but also includes the meaning of “on” something with anintermediate feature or a layer therebetween, and that “above” or “over”not only means the meaning of “above” or “over” something but can alsoinclude the meaning it is “above” or “over” something with nointermediate feature or layer therebetween (i.e., directly onsomething).

The ordinal numbers, such as “first”, “second”, etc., used in thedescription and the claims are used to modify the elements in the claimsand do not themselves imply and represent that the claim has anyprevious ordinal number, do not represent the sequence of some claimedelement and another claimed element, and do not represent the sequenceof the manufacturing methods, unless an addition description isaccompanied. The use of these ordinal numbers is only used to make aclaimed element with a certain name clear from another claimed elementwith the same name.

The term “etch” is used herein to describe the process of patterning amaterial layer so that at least a portion of the material layer afteretching is retained. When “etching” a material layer, at least a portionof the material layer is retained after the end of the treatment. Incontrast, when the material layer is “removed”, substantially all thematerial layer is removed in the process. However, in some embodiments,“removal” is considered to be a broad term and may include etching.

The term “forming” or the term “disposing” are used hereinafter todescribe the behavior of applying a layer of material to the substrate.Such terms are intended to describe any possible layer formingtechniques including, but not limited to, thermal growth, sputtering,evaporation, chemical vapor deposition, epitaxial growth,electroplating, and the like.

Please refer to FIG. 1 . FIG. 1 is a schematic drawing illustrating amemory device 100 according to an embodiment of the present invention.As shown in FIG. 1 , the memory device 100 includes a substrate 10, atleast one memory unit 50, and a first spacer layer 60. The memory unit50 is disposed on the substrate 10, and the memory unit 50 includes afirst electrode 51, a second electrode 53, and a memory material layer52. The second electrode 53 is disposed above the first electrode 51 ina vertical direction (such as a first direction D1 shown in FIG. 1 ),and the memory material layer 52 is disposed between the first electrode51 and the second electrode 53 in the first direction D1. The firstspacer layer 60 is disposed on a sidewall of the memory unit 50 (such asa sidewall SW1 of the first electrode 51, a sidewall SW2 of the secondelectrode 53, and a sidewall of the memory material layer 52). The firstspacer layer 60 includes a first portion P1 and a second portion P2. Thefirst portion P1 is disposed on the sidewall SW1 of the first electrode51, and the second portion P2 is disposed on the sidewall SW2 of thesecond electrode 53. A thickness of the second portion P2 in ahorizontal direction (such as a second direction D2 shown in FIG. 1 ) isgreater than a thickness of the first portion P1 in the second directionD2. The relatively thicker second portion P2 covering the sidewall SW2of the second electrode 53 may be used to improve the protection for thesecond electrode 53 in related manufacturing processes, and themanufacturing yield of the memory device 100 may be enhancedaccordingly.

In some embodiments, the substrate 10 may have a top surface TS and abottom surface BS opposite to the top surface TS in a thicknessdirection of the substrate 10 (such as the first direction D1 shown inFIG. 1 ), and the memory unit 50 and the first spacer layer 60 describedabove may be disposed at a side of the top surface TS, but not limitedthereto. A horizontal direction substantially orthogonal to the firstdirection D1 (such as the second direction D2 described above) may besubstantially parallel with the top surface TS and/or the bottom surfaceBS of the substrate 10, but not limited thereto. Additionally, in thisdescription, a distance between the bottom surface BS of the substrate10 and a relatively higher location and/or a relatively higher part inthe vertical direction (such as the first direction D1) may be greaterthan a distance between the bottom surface BS of the substrate 10 and arelatively lower location and/or a relatively lower part in the firstdirection D1. The bottom or a lower portion of each component may becloser to the bottom surface BS of the substrate 10 in the firstdirection D1 than the top or upper portion of this component. Anothercomponent disposed above a specific component may be regarded as beingrelatively far from the bottom surface BS of the substrate 10 in thefirst direction D1, and another component disposed under a specificcomponent may be regarded as being relatively closer to the bottomsurface BS of the substrate 10 in the first direction D1, but notlimited thereto.

In some embodiments, the memory unit 50 may be a structure with wide topand narrow bottom, and a thickness of the first spacer layer 60surrounding the memory unit 50 in the horizontal direction (such as thesecond direction D2 and other directions perpendicular to the firstdirection D1) may gradually decrease from the top to the bottom.Therefore, the overall width of the memory unit 50 and the first spacerlayer 60 disposed thereon may also have the characteristics of beingwide at the top and narrow at the bottom. In some embodiments, a topwidth of the first electrode 51 (such as a width W2 shown in FIG. 1 )may be greater than a bottom width of the first electrode 51 (such as awidth W1 shown in FIG. 1 ), and a top width of the second electrode 53(such as a width W4 shown in FIG. 1 ) may be greater than a bottom widthof the second electrode 53 (such as a width W3 shown in FIG. 1 ). Awidth of the second electrode 53 (such as the width W3 and/or the widthW4) may be greater than a width of the first electrode 51 (such as thewidth W1 and/or the width W2), and a width of the memory material layer52 may range from the width W2 of the first electrode 51 to the width W3of the second electrode 53, but not limited thereto. In addition, thewidth of each component described above may also be regarded as a lengthof the component in the horizontal direction (such as the seconddirection D2). The memory unit 50 having the structure with wide top andnarrow bottom may be helpful to the formation of the first spacer layer60 including the relatively thicker second portion P2, and some portionsof the first spacer layer 60 may be relatively thinner for avoiding thenegative influence of comprehensively increasing the thickness of thefirst spacer layer 60 on other related manufacturing processes.

In some embodiments, the memory device 100 may further include a secondspacer layer 72 disposed on the first spacer layer 60, and the firstspacer layer 60 may further include a bottom portion BP disposed betweenthe substrate 10 and the second spacer layer 72 in the first directionD1. In some embodiments, the first portion P1, the second portion P2 andthe bottom portion BP of the first spacer layer 60 may be directlyconnected with one another and have an L-shaped structure in across-sectional diagram of the memory device 100 (such as FIG. 1 ), butnot limited thereto. In addition, the thickness of the second portion P2may be greater than the thickness of the first portion P1 and athickness of the bottom portion BP. In some embodiments, the thicknessof the second portion P2 of the first spacer layer 60 may be defined asa distance between a surface of the second portion P2 contacting thesecond electrode 53 and a surface of the second portion P2 contactingthe second spacer layer 72 in the horizontal direction (such as thesecond direction D2), the thickness of the first portion P1 of the firstspacer layer 60 may be defined as a distance between a surface of thefirst portion P1 contacting the first electrode 51 and a surface of thefirst portion P1 contacting the second spacer layer 72 in the horizontaldirection (such as the second direction D2), and the thickness of thebottom portion BP of the first spacer layer 60 may be defined as adistance between a surface of the bottom portion BP contacting thesecond spacer layer 72 and a surface of the bottom portion BP facing thesubstrate 10 in the first direction D1. Additionally, in someembodiments, the top surface of the first spacer layer 60 may be higherthan the top surface of the second electrode 53 in the first directionD1 for ensuring that the second electrode 53 may be completely coveredby the second portion P2 of the first spacer layer 60 in the horizontaldirection (such as the second direction D2 and other directionsperpendicular to the first direction D1), but not limited thereto.

Because of the influence of the shape of the memory unit 50 and theshape of the first spacer layer 60, at least a part of the second spacerlayer 72 may be regarded as a spacer structure 72 s with narrow top andwide bottom, and the bottom portion BP of the first space layer 60 maybe disposed between the substrate 10 and the spacer structure 72S in thefirst direction D1. In some embodiments, a part of the second spacerlayer 72 and/or a part of the spacer structure 72S may be locatedbetween the bottom portion BP of the first spacer layer 60 and the firstportion P1 of the first spacer layer 60 in the first direction D1, andanother part of the second spacer layer 72 and/or another part of thespacer structure 72S may be located between the bottom portion BP of thefirst spacer layer 60 and the second portion P2 of the first spacerlayer 60 in the first direction D1. Additionally, a material compositionof the second spacer layer 72 may be different from a materialcomposition of the first spacer layer 60 for providing required etchingselectivity in the related manufacturing processes. For example, thefirst spacer layer 60 may be made of a nitride dielectric material (suchas silicon nitride) or other suitable dielectric materials, and thesecond space layer 72 may be made of an oxide dielectric material (suchas silicon oxide) or other suitable dielectric materials different fromthe material of the first space layer 60.

In some embodiments, the memory device 100 may include a plurality ofmemory units 50, the corresponding first spacer layers 60, and thecorresponding second spacer layers 72. In addition, the memory device100 may further include a plurality of metal interconnections 40disposed on the substrate 10, and each of the metal interconnections 40may be disposed under one of the memory units 50 and electricallyconnected with the first electrode 51 of the memory unit 50. In someembodiments, each of the metal interconnections 40 may be regarded as avia conductor mainly elongated in the vertical direction (such as thefirst direction D1), but not limited thereto. In some embodiments, eachof the metal interconnections 40 may include a barrier layer 41 and ametal layer 42. The barrier layer 41 may include titanium (Ti), titaniumnitride (TiN), tantalum (Ta), tantalum nitride (TaN) or other suitablebarrier materials, and the metal layer 42 may include tungsten (W),copper (Cu), aluminum (Al), titanium aluminide (TiAl), cobalt tungstenphosphide (CoWP), or other suitable metallic materials.

In some embodiments, the substrate 10 may include a semiconductorsubstrate or a non-semiconductor substrate. The semiconductor substratemay include a silicon substrate, a silicon germanium semiconductorsubstrate, or a silicon-on-insulator (SOI) substrate, and thenon-semiconductor substrate may include a glass substrate, a plasticsubstrate, or a ceramic substrate, but not limited thereto. For example,when the substrate 10 includes a semiconductor substrate, a plurality ofsilicon-based field effect transistors (not illustrated), a dielectriclayer (such as a dielectric layer 11 and a dielectric layer 21 shown inFIG. 1 ) covering the silicon-based field effect transistors, and metalinterconnections 22 may be formed on the semiconductor substrate beforethe step of forming the metal interconnections 40 described above. Insome embodiments, the metal interconnections may be electricallyconnected with some of the metal interconnections 22, respectively, andthe metal interconnections may be electrically connected downward to thesilicon-based field effect transistor described above via some of themetal interconnections 22, but not limited thereto. In some embodiments,each of the metal interconnections 22 may be regarded as a trenchconductor mainly elongated in a horizontal direction. Additionally, insome embodiments, the substrate 10 may include a first region R1 and asecond region R2. The first region R1 may be regarded as a memory cellregion with the memory units 50 disposed thereon, and the second regionR2 may be regarded as a logic region, but not limited thereto. In someembodiments, the region located between the first regions R1 adjacent toeach other may be regarded as a region corresponding to word lines, andthe metal interconnection 22 disposed in this region may include a wordline or electrically connected with a word line, but not limitedthereto.

In some embodiments, the memory device 100 may further include a stoplayer 23, an inter-metal dielectric (IMD) layer 30, a low dielectricconstant (low-k) dielectric layer 74, a stop layer 76, a low-kdielectric layer 78, and a plurality of connection structures (such asconnection structures CS1, a connection structure CS21, a connectionstructure CS22, a connection structure CS31, and a connection structureCS32). The IMD layer 30 may be disposed on the substrate 10 and locatedon the dielectric layer 21. The stop layer 23 may be disposed betweenthe IMD layer 30 and the dielectric layer 21. The metal interconnection40 may penetrate through the IMD layer 30 and the stop layer 23 in thefirst direction D1. The first spacer layer 60 and the second spacerlayer 72 may be disposed on the IMD layer 30 and the metalinterconnections 40. An opening OP may be disposed above the metalinterconnection 22 located between the memory units 50 adjacent to eachother and penetrate through the second space layer 72 and the firstspacer layer 60 in the first direction D1. The low-k dielectric layer 74may be disposed on the IMD layer 30 and the second spacer layer 72, anda part of the low-k dielectric layer 74 may be disposed in the openingOP. The connection structure CS21 may be disposed between the memoryunits 50 adjacent to each other and penetrate through the stop layer 23,the IMD layer 30, and the low-k dielectric layer 74 in the opening OPfor being electrically connected with the metal interconnection 22located between the memory units 50 adjacent to each other. Theconnection structure CS31 may be disposed on the second region R2 andpenetrate through the stop layer 23, the IMD layer 30, and the low-kdielectric layer 74 for being electrically connected with the metalinterconnection 22 on the second region R2.

The stop layer 76 may be disposed on the low-k dielectric layer 74, thesecond spacer layer 72, the first spacer layer 60, a mask layer 54, theconnection structure CS21, and the connection structure CS31, and thelow-k dielectric layer 78 may be disposed on the stop layer 76. Theconnection structure CS1 may penetrate through the low-k dielectriclayer 78, the stop layer 76, and the mask layer 54 on the memory unit 50in the first direction D1 for contacting and being electricallyconnected with the second electrode 53. The connection structure CS22may penetrate through the low-k dielectric layer 78 and the stop layer76 on the connection structure CS21 in the first direction D1 forcontacting and being electrically connected with the connectionstructure CS21. The connection structure CS32 may penetrate through thelow-k dielectric layer 78 and the stop layer 76 on the connectionstructure CS31 in the first direction D1 for contacting and beingelectrically connected with the connection structure CS31. In someembodiments, each of the connection structures described above (such asthe connection structure CS1, the connection structure CS21, theconnection structure CS22, the connection structure CS31, and/or theconnection structure CS32) may include a via conductor and a trenchconductor disposed on and connected with the via conductor, but notlimited thereto.

In some embodiments, the structure of each of the metal interconnections22 and the structure of each of the connection structures (such as theconnection structure CS1, the connection structure CS21, the connectionstructure CS22, the connection structure CS31, and/or the connectionstructure CS32) may be similar to that of the metal interconnection 40and include a barrier layer (not illustrated) and a metal layer (notillustrated), but not limited thereto. In some embodiments, thedielectric layer 11, the dielectric layer 21, and the IMD layer 30 mayrespectively include silicon oxide, a low-k dielectric material, orother suitable dielectric materials. The low-k dielectric layer 74 andthe low-k dielectric layer 78 may respectively include a dielectricmaterial with a dielectric constant lower than 2.7, such asbenzocyclclobutene (BCB), hydrogen silsesquioxane (HSQ), methylsilesquioxane (MSQ), hydrogenated silicon oxycarbide (SiOC—H), a porousdielectric material, or other suitable dielectric materials. The stoplayer 23 and the stop layer 76 may respectively include nitrogen dopedcarbide (NDC), silicon nitride, silicon carbon-nitride (SiCN), or othersuitable insulation materials.

In some embodiments, the first electrode 51 and the second electrode 53in each of the memory units 50 may respectively include aluminum,platinum, ruthenium, iridium, nickel, cobalt, chromium, tungsten,copper, hafnium, zirconium, zinc, gold, titanium, an alloy of thematerial described above, a mixture of the material described above, orother suitable metallic electrically conductive materials ornon-metallic electrically conductive materials. The memory materiallayer 52 in each of the memory units 50 may include a variableresistance material, a phase change material, or other suitablematerials capable of providing memory operations by changing state. Thevariable resistance material described above may include metal oxidesuch as transition metal oxide, perovskite oxide, or other suitablevariable resistance materials. The phase change material described abovemay include germanium antimony telluride (Ge₂Sb₂Te₅, GST) or othersuitable phase change materials. When the memory material layer 52 is avariable resistance material, the memory unit 50 may be regarded as aresistive memory unit, and the memory material layer 52 may be regardedas a switching medium in the resistive memory unit. The resistance ofthe resistive memory unit may be changed by applying suitable voltage tothe top electrode and the bottom electrode (such as the second electrode53 and the first electrode 51) in the stacked structure, and theresistive memory unit may switch to high resistance state (HRS) or lowresistance state (LRS) for realizing the operation mode of the memorydevice, such as storing data, reading data, and resetting.

Please refer to FIGS. 2-6 and FIG. 1 . FIGS. 2-6 are schematic drawingsillustrating a manufacturing method of a memory device according to anembodiment of the present invention, wherein FIG. 3 is a schematicdrawing in a step subsequent to FIG. 2 , FIG. 4 is a schematic drawingin a step subsequent to FIG. 3 , FIG. 5 is a schematic drawing in a stepsubsequent to FIG. 4 , FIG. 6 is a schematic drawing in a stepsubsequent to FIG. 5 , and FIG. 1 may be regarded as a schematic drawingin a step subsequent to FIG. 6 , but not limited thereto. As shown inFIG. 1 , the manufacturing method of the memory device 100 in thisembodiment may include the following steps. The memory unit 50 is formedon the substrate 10, and the memory unit 50 includes the first electrode51, the second electrode 53, and the memory material layer 52. Thesecond electrode 53 is disposed above the first electrode 51 in thefirst direction D1, and the memory material layer 52 is disposed betweenthe first electrode 51 and the second electrode 53 in the firstdirection D1. The first spacer layer 60 is formed on the sidewall of thememory unit 50, and the first spacer layer 60 includes the first portionP1 and the second portion P2. The first portion P1 is disposed on thesidewall SW1 of the first electrode 51, and the second portion P2 isdisposed on the sidewall SW2 of the second electrode 53. The thicknessof the second portion P2 in a horizontal direction (such as the seconddirection D2) is greater than the thickness of the first portion P1 inthe second direction D2.

Specifically, the manufacturing method of the memory device in thisembodiment may include but is not limited to the following steps.Firstly, as shown in FIG. 2 , the dielectric layer 11, the dielectriclayer 21, the metal interconnections 22, the stop layer 23, the IMDlayer 30, the metal interconnections 40, and the memory units 50 areformed on the substrate 10. In some embodiments, a stacked materiallayer used to form the memory units 50 may be formed on the metalinterconnections 40 and the IMD layer 30, and the mask layer 54 may beformed on the stacked material layer. Subsequently, the mask layer 54and/or a patterned photoresist layer (not illustrated) may be used as anetching mask for performing an etching process to the stacked materiallayer and forming the memory units 50. The mask layer 54 may include anoxide insulation material or other suitable insulation materials. Theetching process described above may include a reactive ion etching (ME)process or other suitable etching approaches. Additionally, in someembodiments, a lateral trimming process 91 may be performed and used toetch the memory unit 50 for making the memory unit 50 having theabove-mentioned structure with wide top and narrow bottom, and thetrimming process 91 may be performed in the etching process describedabove and/or after the etching process described above. For example, thetrimming process 91 may be an etching step in the ME etching process,and the lateral etching performance may be modified by tuning theetching parameters (such as reducing the etching effect generated bypolymer) for forming the memory unit 50 having the structure with widetop and narrow bottom. In some embodiments, the memory unit 50 havingthe structure with wide top and narrow bottom may also be formed byperforming the trimming process 91 with material selection and matchingof the first electrode 51 and the second electrode 53. In other words,the material composition of the second electrode 53 may be differentfrom the material composition of the first electrode 51, and the rate ofetching the first electrode 51 in the trimming process 91 may beslightly higher than the rate of etching the second electrode 53 in thetrimming process 91, but not limited thereto.

Subsequently, as shown in FIG. 3 , the first spacer layer 60 is formedon the IMD layer 30, the metal interconnections 40, the memory units 50,and the mask layers 54. In some embodiments, because of the influence ofthe memory unit 50 having the structure with wide top and narrow bottom,the first spacer layer 60 formed on the memory units 50 and the masklayers 54 may have overhang structures OS. For example, the first spacerlayer 60 may include the first portion P1, the second portion P2, athird portion P3, and the bottom portion BP. The first portion P1 may bedisposed on the sidewall SW1 of the first electrode 51, the secondportion P2 may be disposed on the sidewall SW2 of the second electrode53, the third portion P3 may be disposed above the memory unit 50 andthe mask layer 54 in the first direction D1, and the bottom portion BPmay be disposed on the IMD layer 30 and the metal interconnections 40.The third portion P3 may be directly connected with the second portionP2, the second portion P2 may be directly connected with the firstportion P1, and the first portion P1 may be directly connected with thebottom portion BP. Because of the memory unit 50 having the structurewith wide top and narrow bottom and/or by modifying the processparameters of the film forming process of the first spacer layer 60, thethird portion P3 and the second portion P2 may be relatively thicker,the first portion P1 and the bottom portion BP may be relativelythinner, and the third portion P3 and a part of the second portion P2may form the overhang structure OS on the memory unit 50.

Subsequently, as shown in FIG. 4 and FIG. 5 , the spacer structure 72Sis formed on the first spacer layer 60. The method of forming the spacerstructure 72S may include but is not limited to the following steps. Asshown in FIG. 4 , the second spacer layer 72 may be formed on the firstspacer layer 60, and the space between the memory units 50 adjacent toeach other may be filled with the second spacer layer 72. As shown inFIG. 4 and FIG. 5 , an etching process 92 may be performed after thesecond spacer layer 72 is formed, and at least a part of the secondspacer layer 72 may be etched by the etching process 92 to be the spacerstructure 72S. In some embodiments, at least an etching step in theetching process 92 may be regarded as an etching back process for thesecond spacer layer 72 so as to form the opening OP by removing a partof the second spacer layer 72 (such as the second spacer layer 72 on thememory unit 50 in the first direction D1) and a part of the bottomportion BP of the first spacer layer 60. The opening OP may be locatedbetween the memory units 50 adjacent to each other in the seconddirection D2, and the opening OP may penetrate through the second spacerlayer 72 and the first spacer layer 60 in the first direction D1 forexposing a part of the IMD layer 30.

In some embodiments, at least a part of the third portion P3 of thefirst spacer layer 60 may be located between the second spacer layer 72and the memory unit 50 in the first direction D1 before the etchingprocess 92, and the third portion P3 of the first spacer layer 60 may beremoved by the etching process 92. In addition, the second electrode 53may be completely covered by the second portion P2 of the first spacerlayer 60 in the horizontal direction (such as the second direction D2)before and after the etching process 92 for protecting the secondelectrode 53. The problem that the sidewall of the second electrode 53is exposed by over etching the first spacer layer 60 in the etchingprocess 92 may be improved because the overhang structure OS isrelatively thicker. The mask layer 54 may cover the top surface of thesecond electrode 53 before and after the etching process 92, and thesecond electrode 53 may be protected by the first spacer layer 60 andthe mask layer 54 encompassing the second electrode 53 accordingly.Additionally, the opening OP is formed by the etching process 92, therequired etching strength of the etching process 92 may be reducedbecause the bottom portion BP of the first spacer layer 60 is relativelythinner, and the part of the second portion P2 of the first spacer layer60 etched in the etching process 92 may be relatively reducedaccordingly for ensuring that the second electrode 53 is completelycovered by the second portion P2 of the first space layer 60 in thehorizontal direction. In other words, when the thickness of the firstspace layer is increased comprehensively, the etching strength has to berelatively increased (such as increasing the etching time) for formingthe opening OP penetrating through the first spacer layer 60, the secondelectrode 53 might be exposed because more of the first spacer layer 60on the sidewall of the second electrode 53 is etched accordingly, andrelated manufacturing defects may be generated.

In some embodiments, the etching process 92 may be further used toremove the second spacer layer 72 and the first spacer layer 60 abovethe second region R2 for exposing the IMD layer 30 above the secondregion R2. Subsequently, as shown in FIG. 5 and FIG. 6 , the low-kdielectric layer 74, the connection structure CS21, and the connectionstructure CS31 descried above may be formed. In some embodiments, aplanarization process may be carried out after the step of forming thelow-k dielectric layer 74 and before the step of forming the connectionstructure CS21 and the connection structure CS31 for making the topsurface of the low-k dielectric layer 74, the top surface of the spacerstructure 72S, the top surface of the first spacer layer 60, and the topsurface of the mask layer substantially coplanar, but not limitedthereto. Subsequently, as shown in FIG. 6 and FIG. 1 , the stop layer76, the low-k dielectric layer 78, the connection structures CS1, theconnection structure CS22, and the connection structure CS32 describedabove may be formed for forming the memory device 100 shown in FIG. 1 .

To summarize the above descriptions, in the memory device and themanufacturing method thereof according to the present invention, thefirst spacer layer having the overhang structures may be formed on thememory units for forming the relatively thicker first spacer layer onthe sidewall of the second electrode and enhancing the performance ofprotecting the memory unit in the subsequent manufacturing processes,and the manufacturing yield of the memory device may be improvedaccordingly.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A memory device, comprising: a substrate; amemory unit disposed on the substrate, wherein the memory unitcomprises: a first electrode; a second electrode disposed above thefirst electrode in a vertical direction; and a memory material layerdisposed between the first electrode and the second electrode in thevertical direction; and a first spacer layer disposed on a sidewall ofthe memory unit, wherein the first spacer layer comprises: a firstportion disposed on a sidewall of the first electrode; and a secondportion disposed on a sidewall of the second electrode, wherein athickness of the second portion in a horizontal direction is greaterthan a thickness of the first portion in the horizontal direction, andthe second electrode is completely covered by the second portion of thefirst spacer layer in the horizontal direction.
 2. The memory deviceaccording to claim 1, further comprising: a second spacer layer disposedon the first spacer layer, wherein a material composition of the secondspacer layer is different from a material composition of the firstspacer layer.
 3. The memory device according to claim 2, wherein thefirst spacer layer further comprises a bottom portion disposed betweenthe substrate and the second spacer layer in the vertical direction. 4.The memory device according to claim 3, wherein a part of the secondspacer layer is located between the bottom portion of the first spacerlayer and the first portion of the first spacer layer in the verticaldirection.
 5. The memory device according to claim 3, wherein a part ofthe second spacer layer is located between the bottom portion of thefirst spacer layer and the second portion of the first spacer layer inthe vertical direction.
 6. The memory device according to claim 1,wherein a top width of the first electrode is greater than a bottomwidth of the first electrode.
 7. The memory device according to claim 1,wherein a top width of the second electrode is greater than a bottomwidth of the second electrode.
 8. The memory device according to claim1, wherein a width of the second electrode is greater than a width ofthe first electrode.
 9. The memory device according to claim 1, whereinthe memory material layer comprises a variable resistance material or aphase change material.
 10. A manufacturing method of a memory device,comprising: forming a memory unit on a substrate, wherein the memoryunit comprises: a first electrode; a second electrode disposed above thefirst electrode in a vertical direction; and a memory material layerdisposed between the first electrode and the second electrode in thevertical direction; and forming a first spacer layer on a sidewall ofthe memory unit, wherein the first spacer layer comprises: a firstportion disposed on a sidewall of the first electrode; and a secondportion disposed on a sidewall of the second electrode, wherein athickness of the second portion in a horizontal direction is greaterthan a thickness of the first portion in the horizontal direction, andthe second electrode is completely covered by the second portion of thefirst spacer layer in the horizontal direction.
 11. The manufacturingmethod of the memory device according to claim 10, wherein the firstspacer layer further comprises a third portion disposed above the memoryunit in the vertical direction and connected with the second portion ofthe first spacer layer.
 12. The manufacturing method of the memorydevice according to claim 11, wherein the third portion of the firstspacer layer and a part of the second portion of the first spacer layerform an overhang structure on the memory unit.
 13. The manufacturingmethod of the memory device according to claim 11, further comprising:forming a spacer structure on the first spacer layer, wherein a methodof forming the spacer structure comprises: forming a second spacer layeron the first spacer layer; and performing an etching process after thesecond spacer layer is formed, wherein at least a part of the secondspacer layer is etched by the etching process to be the spacerstructure.
 14. The manufacturing method of the memory device accordingto claim 13, wherein at least a part of the third portion of the firstspacer layer is located between the second spacer layer and the memoryunit in the vertical direction before the etching process, and the thirdportion of the first spacer layer is removed by the etching process. 15.The manufacturing method of the memory device according to claim 13,wherein the second electrode is completely covered by the second portionof the first spacer layer in the horizontal direction before and afterthe etching process.
 16. The manufacturing method of the memory deviceaccording to claim 13, wherein a material composition of the secondspacer layer is different from a material composition of the firstspacer layer.
 17. The manufacturing method of the memory deviceaccording to claim 13, wherein the first spacer layer further comprisesa bottom portion disposed between the substrate and the spacer structurein the vertical direction.
 18. The manufacturing method of the memorydevice according to claim 17, wherein a part of the spacer structure islocated between the bottom portion of the first spacer layer and thefirst portion of the first spacer layer in the vertical direction. 19.The manufacturing method of the memory device according to claim 17,wherein a part of the spacer structure is located between the bottomportion of the first spacer layer and the second portion of the firstspacer layer in the vertical direction.